It's a pretty recent development, but have you tried Django 1.8's Conditional Aggregation and Conditional Expression features? https://docs.djangoproject.com/e

It's a pretty recent development, but have you tried Django 1.8's Conditional Aggregation and Conditional Expression features? https://docs.djangoproject.com/en/1.8/ref/models/conditional-expressions/#conditional-aggregation https://docs.djangoproject.com/en/1.8/ref/models/conditional...